The Long Term Evolution (LTE) project is an evolution of 3rd generation (3G) mobile communications, which improves and enhances the 3G radio access technologies and applies the orthogonal frequency division multiplexing (OFDM) technology and the multiple-input multiple-output (MIMO) technology. An LTE system is capable of providing a peak rate of 100 Mbit/s for downlink transmission and 50 Mbit/s for uplink transmission under a spectral bandwidth of 20 MHz, thus improving the performance of user equipments (UEs) at cell edges, increasing the cell capacity, and decreasing the system delay.
The cell relation is always a focus in radio network system planning and optimization, and mainly includes two major categories: (a) neighbor relation; and (b) non-neighbor relation (abnormal neighbor relation under cross coverage and normal non-neighbor relation).
Earlier neighbor relations are more often established as follows. On the basis of principles for establishing neighbor relations, a neighbor relation list is set on a radio network controller (RNC) in advance, and then the RNC delivers neighbor information to a UE by delivering a measurement control message to perform a customized neighbor quality detection to facilitate a handover decision.
Unlike neighbor planning methods of earlier systems such as Wideband Code Division Multiple Access (WCDMA), an automatic neighbor relation (ANR) function in an LTE self-organizing network realizes establishment and maintenance of an ANR. The function focuses more on automatic detection of a cell and reporting to an evolved NodeB (eNB) by a UE, as well as detection, creation, and deletion of the neighbor relation by the eNB, thereby avoiding wrong addition of a neighbor due to such possible issues as pilot leakage when the eNB adds a neighbor relation, so that the decision on the quality and stability of the system will not be affected.
Currently, the ANR workflow of an LTE self-organizing network is as follows. A UE sends a detected physical cell identity (PCI) of cell B to cell A; if the PCI is unidentifiable, the UE is instructed to read a Public Land Mobile Network (PLMN) list, a global cell identity (GCI, that is, PLMN identity+eNB identity+cell identity), a type approval code (TAC), a resource admission and control (RAC) code, and other broadcast messages corresponding to the PCI; and the UE reads and reports the broadcast messages of cell B. The above flow is applicable to the reading of a broadcast message of an intra-frequency, inter-frequency, or inter-system
Currently, the ANR function reads a broadcast message of an unknown neighboring cell (that is, a cell whose PCI is unidentifiable) in two ways: discontinuous reception (DRX) and measurement gap (GAP).
If only the DRX is used, when there is no enough uplink or downlink data source, the UE has more free time to read a broadcast message, and can successfully read a broadcast message (such as a GCI) of an inter-frequency or inter-system. However, when the uplink or downlink data volume is relatively sufficient, the free time for the UE to read a broadcast message decreases, so the probability of successfully reading a broadcast message of an inter-frequency or inter-system cell decreases accordingly.
If only the GAP is used, because only fixed 6 ms in a specified cycle of 40 ms is used for reading a broadcast message of an inter-frequency or inter-system cell, the probability of successfully reading a broadcast message by the UE is relatively low; moreover, the cycles of broadcast messages of different inter-system cells are different; therefore, this way of reading is not compatible with the reading of all inter-system broadcast messages.
Therefore, it is currently a pressing issue in the field of mobile communications how to enable a UE to quickly read a broadcast message of an unknown neighboring cell and report the message to an eNB in order to discover a new neighbor in a timely manner and create a neighbor relation.